3.1.1.1.6 NineGrid Bitmap Cache

The NineGrid bitmap cache is used to store NineGrid-compliant bitmaps. There is only one cache for all NineGrid bitmaps. The individual bitmap sizes are variable and depend on the bitmap dimensions.

The total cache size and cache entries are capped by the DrawNineGrid Cache Capability Set (section 2.2.1.2). The default size of the cache is 2.5 MB for 8 bpp, 5 MB for 16 bpp, or 7.5 MB for 24 bpp. The default number of allowed cache entries is 256.

The Create NineGrid Bitmap (section 2.2.2.2.1.3.4), Stream Bitmap First (section 2.2.2.2.1.3.5.1), and Stream Bitmap Next (section 2.2.2.2.1.3.5.2) Alternate Secondary Drawing Orders are used to populate the NineGrid Bitmap Cache. Individual bitmaps within the cache are rendered with the DrawNineGrid (section 2.2.2.2.1.1.2.21) Primary Drawing Order. This primary drawing order applies a NineGrid algorithm to the bitmap before rendering it (for an example rendering, see section 4.4).